Using physics to understand the ‘music’ of the brain

09.08.2018

In a nutshell: A physics-based approach successfully explains mysterious oscillations in brain activity that are like the notes produced by a musical instrument.

Our understanding of how the brain works has been based mostly on observation, with little ability to predict behaviour or analyse its underlying mechanisms. Techniques such as electroencephalography (EEG) are used to measure electrical activity in the brain and link it to brain function – or dysfunction.

When the cerebral cortex is stimulated in one location by randomly flickering light, EEG recordings show that the resulting brain activity oscillates in other locations in a way that is closely related to changes in the light. These oscillations, known as perceptual echo, were first discovered in 2012 but have remained a mystery ever since.

Perceptual echo might have implications for the processes involved in visual perception, so learning more about it could increase our understanding of human vision. However, there have been no studies to predict perceptual echo or analyse its underlying mechanisms.

Brain Function CoE Chief Investigator Peter Robinson and his colleagues from the University of Sydney aimed to fill this gap using neural field theory – a comprehensive model of the connections between brain stimuli, activity and measurements that is based on physics rather than statistics.

The researchers used neural field theory to predict the frequency and spatial patterns of perceptual echo by splitting the brain’s oscillations into ‘natural modes’ (like the notes produced by a musical instrument) and their patterns on the cortex – as shown in the illustration, where strong oscillations in the visual cortex are shown in red. They found that two modes dominated, which closely matched experimental observations. This finding is comparable to striking a musical instrument, such as a drum: even if you hit it randomly, the resulting sound will be dominated by its favoured notes.

The team’s work – which combined theory, experiment, and physical and biological sciences – demonstrates the power of interdisciplinary methods to explain brain activity.

Next steps:The team is using the same approach to extract information about brain structure (which is difficult to observe) from brain activity (which is easier to observe), which they hope will enable them to explain a range of other brain phenomena. This approach is like ‘hearing’ the shape of a drum from the sounds it produces.